The present invention relates to a catalyst for polyester production, a process for producing a polyester using the catalyst, a polyester obtained by the process and uses of the polyester.
Because of their excellent mechanical strength, heat resistance, transparency and gas barrier properties, polyesters such as polyethylene terephthalate are favorably used as not only materials of containers of various beverages such as juice, soft drinks and carbonated beverages but also materials of films, sheets and fibers.
The polyesters can be generally produced using, as starting materials, dicarboxylic acids such as aromatic dicarboxylic acids and diols such as aliphatic diols. In more detail, a dicarboxylic acid and a diol are first subjected to esterification reaction to form a low condensate (low molecular weight polyester), and the low condensate is then subjected to deglycolation reaction (liquid phase polycondensation) to increase the molecular weight. In some cases, solid phase polycondensation is performed to further increase the molecular weight.
In the process for producing polyesters mentioned above, a conventional antimony compound, a conventional germanium compound or the like is used as a polycondensation catalyst.
However, the polyester produced by the use of the antimony compound as a polycondensation catalyst is inferior to the polyester produced by the use of a germanium compound as a polycondensation catalyst in the transparency and the heat resistance. In the use of the antimony compound as a polycondensation catalyst, further, the acetaldehyde content in the resulting polyester is desired to be decreased.
On the other hand, the germanium compound is considerably expensive, so that the production cost of polyester becomes high. To decrease the production cost, a process including recovering the germanium compound scattered during the polycondensation and reusing it has been studied.
By the way, it is known that titanium is an element having a function of promoting polycondensation reaction of a low condensate. Titanium compounds such as titanium alkoxide, titanium tetrachloride, titanyl oxalate and orthotitanic acid are publicly known as polycondensation catalysts, and various studies have been made to utilize such titanium compounds as the polycondensation catalysts.
However, when the conventional titanium compounds are used as the polycondensation catalysts, their activity is inferior to that of the antimony compounds or the germanium compounds. In addition, the resulting polyester has a problem of being markedly colored yellow, and hence they have not been put into practical use yet. In the industrial production of polyesters using these titanium compounds as the polycondensation catalysts, further, there is a problem of corrosion caused by elution of chlorine content in case of catalysts containing a large amount of chlorine, such as titanium tetrachloride and partial hydrolyzate of titanium tetrachloride. Therefore, catalysts having low chlorine content are sometimes desired.
Under such circumstances as described above, catalysts for polyester production capable of producing polyesters with high polycondensation activity or catalysts for polyester production capable of producing such polyesters as satisfy any one of requirements of low acetaldehyde content, high transparency and excellent tint with high catalytic activity are desired.
There are also desired a process for producing polyesters by which polyesters having desired intrinsic viscosity (IV) can be obtained for a short period of time, a process for producing polyesters by which polyesters having low acetaldehyde content can be obtained with high polymerization activity, and a process for producing polyesters by which polyesters having excellent tint can be obtained with high polymerization activity.
As described above, the polyester, particularly polyethylene terephthalate, is favorably used as a material of containers of beverages such as juice, soft drinks and carbonated beverages.
To produce a blow molded article from the polyester, the polyester is fed to a molding machine such as an injection molding machine to form a preform for a blow molded article, then the preform is inserted in a mold of a given shape, and the preform is subjected to stretch blow molding and a heat treatment (heat setting).
As for the molded product obtained from the conventional polyester such as conventional polyethylene terephthalate, however, the content of acetaldehyde is increased during the molding and the acetaldehyde remains in the resulting molded product, so that flavor or scent of the contents filled in the molded product is sometimes considerably deteriorated.
As a process for producing polyethylene terephthalate having small increase of the acetaldehyde content during the molding, a process, which includes treating a particulate polyethylene terephthalate with water vapor of 110xc2x0 C. or higher prior to solid phase polycondensation of the polyethylene terephthalate, is disclosed in Japanese Patent Laid-Open Publication No. 25815/1984, or a process for producing polyethylene terephthalate of high polymerization degree, which includes a step of moisture controlling polyethylene terephthalate having an intrinsic viscosity of not less than 0.4 dl/g and a density of not more than 1.35 g/cm3 to vary the moisture content to not less than 0.2% by weight, a step of precrystallizing the polyethylene terephthalate at a temperature of 140xc2x0 C. or higher, and a step of solid phase polymerization at a temperature of 180 to 240xc2x0 C. in an inert gas atmosphere or reduced pressure, is disclosed in Japanese Patent Laid-Open Publication No. 219328/1984.
However, the increase of the acetaldehyde content in the polyethylene terephthalate obtained by these processes cannot be lowered down below a certain level.
In Japanese Patent Laid-Open Publication No. 97990/1993, a method for treating polyethylene terephthalate comprising bringing pellets of polyethylene terephthalate having been subjected to solid phase polymerization into contact with a phosphoric acid aqueous solution having a concentration of not less than 1 ppm is disclosed.
In this method, however, the phosphoric acid functions as an acid catalyst to perform hydrolysis, and as a result, decrease of the intrinsic viscosity is accelerated during the melt molding.
The conventional polyester, e.g., polyethylene terephthalate, contains oligomers such as a cyclic trimer, and the oligomers such as a cyclic trimer adhere to an inner surface of a mold for blow molding or a gas exhaust vent or a gas exhaust pipe of a mold to cause stain of the mold, or adhere to a vent zone of an injection molding machine. The stain of the mold causes surface roughening or whitening of the resulting blow molded article. The whitened blow molded article must be discarded. In the production of a blow molded article using the conventional polyester, the stain of the mold must be frequently removed, and this results in conspicuous lowering of productivity of the blow molded article.
In addition, the polyester obtained by the use of the antimony compound or the germanium compound as a polycondensation catalyst sometimes has low melt flowability and is insufficient in the moldability.
Under such circumstances as described above, there is desired a polyester having a low acetaldehyde content, hardly increased in the acetaldehyde content during the molding and hardly causing stain of a mold or a polyester having high melt flowability and excellent moldability.
Further, there is also desired a polyester molded product having excellent transparency and tint or a molded product such as a blow molded article preform or a blow molded article, e.g., a polyester blow molded article having a low content of a cyclic trimer.
One of the present applicants has found that the main cause of the stain of a mold in the molding process resides in that large amounts of oligomers such as a cyclic trimer are produced in the molding of the polyester to increase the total amount of the oligomers such as a cyclic trimer contained in the polyester, and has also found that the increase of the oligomers such as a cyclic trimer can be remarkably inhibited by bringing the polyester obtained through the solid phase polycondensation into contact with water or the like, so that they have proposed this in Japanese Patent Laid-Open Publication No. 283393/1996.
The present invention has been made in view of the prior arts as described above, and it is an object of the invention to provide a catalyst for polyester production capable of producing a polyester with high catalytic activity or a catalyst for polyester production capable of producing such a polyester of high quality as satisfies any one of requirements of a low acetaldehyde content, high transparency and excellent tint with high catalytic activity.
It is another object of the invention to provide a process for producing a polyester by which a polyester having a desired intrinsic viscosity (IV) can be obtained for a short period of time, a process for producing a polyester by which a polyester having a low acetaldehyde content can be produced with high polymerization activity, and a process for producing a polyester by which a polyester having excellent tint can be obtained with high polymerization activity.
It is a further object of the invention to provide a polyester having small increase of the acetaldehyde content during the molding, particularly a polyester having a low acetaldehyde content and small increase of the acetaldehyde content during the molding, a polyester hardly bringing about stain of a mold, a polyester having excellent transparency and tint, or a polyester having high melt flowability and excellent moldability.
It is a still further object of the invention to provide a polyester molded product having excellent transparency and tint or a polyester molded product such as a blow molded article preform or a blow molded article, e.g., a polyester blow molded article having a low content of a cyclic trimer.
One embodiment of the catalyst for polyester production according to the present invention includes:
a catalyst for polyester production, comprising a solid titanium compound (I-a) which is obtained by dehydro-drying a hydrolyzate obtained by hydrolyzing a titanium halide and has a molar ratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) exceeding 0.09 and less than 4;
a catalyst for polyester production, comprising a titanium-containing solid compound (I-b) which is obtained by dehydro-drying a hydrolyzate obtained by hydrolyzing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound and has a molar ratio (OH/Ti) of a hydroxyl group (OH) to titanium (Ti) exceeding 0.09 and less than 4; and
a catalyst for polyester production, comprising:
(I) a polycondensation catalyst component comprising the solid titanium compound (I-a) and/or the titanium-containing solid compound (I-b), and (II) a co-catalyst component comprising a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimony and phosphorus.
Another embodiment of the catalyst for polyester production according to the present invention includes:
a catalyst for polyester production, comprising:
(I) a polycondensation catalyst component comprising a solid titanium compound (I-c) obtained by dehydro-drying a hydrolyzate obtained by hydrolyzing a titanium halide, and
(II) a co-catalyst component comprising a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimony and phosphorus;
a catalyst for polyester production, comprising a titanium-containing solid compound (I-d) obtained by dehydro-drying a hydrolyzate obtained by hydrolyzing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound; and
a catalyst for polyester production, comprising:
(I) a polycondensation catalyst component comprising the titanium-containing solid compound (I-d), and
(II) a co-catalyst component comprising a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimony and phosphorus.
In the catalyst for polyester production described above, the co-catalyst component (II) is preferably a magnesium compound.
A further embodiment of the catalyst for polyester production according to the present invention includes:
a catalyst for polyester production, comprising a solid titanium compound (I-e) obtained by a process comprising brining a titanium halide into contact with water to hydrolyze the titanium halide and thereby obtain an acid solution containing a hydrolyzate of the titanium halide, rendering the solution basic by the use of a base, then adjusting pH of the solution to 2 to 6 by the use of an acid, and dehydro-drying the resulting precipitate;
a catalyst for polyester production, comprising a solid titanium compound (I-f) obtained by a process comprising bringing a titanium halide into contact with water to hydrolyze the titanium halide and thereby obtain an acid solution containing a hydrolyzate of the titanium halide, adjusting pH of the solution to 2 to 6 by the use of a base, and dehydro-drying the resulting precipitate;
a catalyst for polyester production, comprising:
(I) a polycondensation catalyst component comprising the solid titanium compound (I-e) or the solid titanium compound (I-f), and
(II) a co-catalyst component comprising a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimony and phosphorus;
a catalyst for polyester production, comprising a titanium-containing solid compound (I-g) obtained by a process comprising bringing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound into contact with water to hydrolyze the titanium halide and thereby obtain an acid solution containing a hydrolyzate of the titanium halide, rendering the solution basic by the use of a base, then adjusting pH of the solution to 2 to 6 by the use of an acid, and dehydro-drying the resulting precipitate;
a catalyst for polyester production, comprising a titanium-containing solid compound (I-h) obtained by a process comprising bringing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound into contact with water to hydrolyze the titanium halide and thereby obtain an acid solution containing a hydrolyzate of the titanium halide, adjusting pH of the solution to 2 to 6 by the use of a base, and dehydro-drying the resulting precipitate;
a catalyst for polyester production, comprising:
(I) a polycondensation catalyst component comprising the titanium-containing solid compound (I-g) or (I-h), and
(II) a co-catalyst component comprising a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimony and phosphorus.
In the catalyst for polyester production described above, the co-catalyst component (II) is preferably a magnesium compound.
A still further embodiment of the catalyst for polyester production according to the present invention includes:
a catalyst for polyester production, comprising a solid titanium compound (I-i) which is obtained by dehydro-drying titanium hydroxide and has a crystallinity, as calculated from an X-ray diffraction pattern having 2xcex8 (diffraction angle) of 18xc2x0 to 35xc2x0, of not more than 50%; and
a catalyst for polyester production, comprising:
(I) a polycondensation catalyst component comprising the solid titanium compound (I-i), and
(II) a co-catalyst component comprising a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimony and phosphorus.
A still further embodiment of the catalyst for polyester production according to the present invention includes:
a catalyst for polyester production, comprising a slurry obtained by heating a mixture of:
(A-1) a hydrolyzate (I-j) obtained by hydrolyzing a titanium compound or a hydrolyzate (I-k) obtained by hydrolyzing a mixture of a titanium compound and a compound of at least one element selected from elements other than titanium or a precursor of the compound,
(B) a basic compound, and
(C) an aliphatic diol.
In the catalyst for polyester production described above, the basic compound (B) is preferably at least one compound selected from tetraethylammonium hydroxide, tetramethylammonium hydroxide, aqueous ammonia, sodium hydroxide, potassium hydroxide, N-ethylmorpholine and N-methylmorpholine.
The aliphatic diol (C) is preferably ethylene glycol.
A still further embodiment of the catalyst for polyester production according to the present invention includes:
a catalyst for polyester production, comprising:
(A-2) a hydrolyzate (I-m) obtained by hydrolyzing a titanium halide or a hydrolyzate (I-n) obtained by hydrolyzing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound, and
(D) a metallic phosphate containing at least one element selected from beryllium, magnesium, calcium, strontium, boron, aluminum, gallium, manganese, cobalt and zinc; and
a catalyst for polyester production, comprising a slurry obtained by heating a mixture of:
(A-2) a hydrolyzate (I-m) obtained by hydrolyzing a titanium halide or a hydrolyzate (I-n) obtained by hydrolyzing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound,
(E) a metallic compound containing at least one element selected from beryllium, magnesium, calcium, strontium, boron, aluminum, gallium, manganese, cobalt and zinc,
(F) at least one phosphorus compound selected from phosphoric acid and phosphoric esters, and
(G) an aliphatic diol.
In the catalyst for polyester production described above, the metallic phosphate (D) is preferably magnesium hydrogenphosphate or trimagnesium diphosphate. Further, it is preferable that the metallic compound (E) is a magnesium compound, the phosphorus compound (F) is phosphoric acid or trimethyl phosphate, and the aliphatic diol (G) is ethylene glycol.
The heating temperature of the mixture of the components (A-2), (E), (F) and (G) is preferably in the range of 100 to 200xc2x0 C., and the heating time is preferably in the range of 3 minutes to 5 hours.
In the catalyst for polyester production according to the invention described above, the compound of at least one element selected from elements other than titanium or the precursor of the compound is a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, copper, zinc, boron, aluminum, gallium, silicon, germanium, tin, antimony and phosphorus, or a precursor of the compound.
One embodiment of the process for producing a polyester according to the present invention is a process comprising polycondensing an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof in the presence of the above-mentioned catalyst for polyester production.
Another embodiment of the process for producing a polyester according to the present invention is a process comprising an esterification step in which an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof are esterified to form a low condensate and a polycondensation step in which the low condensate is polycondensed in the presence of a polycondensation catalyst to increase the molecular weight, wherein:
the polycondensation catalyst used is a catalyst comprising:
(I) a polycondensation catalyst component comprising a hydrolyzate (I-j) obtained by hydrolyzing a titanium compound or a hydrolyzate (I-k) obtained by hydrolyzing a mixture of a titanium compound and a compound of at least one element selected from elements other than titanium or a precursor of the compound, and
(II) a co-catalyst component comprising a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimony and phosphorus; and
the polycondensation catalyst component (I) is added to the esterification reactor before the beginning of the esterification reaction or immediately after the beginning of the esterification reaction.
In the process for producing a polyester described above, the co-catalyst component (II) is preferably a magnesium compound.
A further embodiment of the process for producing a polyester according to the present invention is a process comprising polycondensing an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof in the presence of a polycondensation catalyst selected from the following catalysts (1) to (3) and a phosphoric ester to produce a polyester;
(1) a polycondensation catalyst comprising a hydrolyzate (I-m) obtained by hydrolyzing a titanium halide,
(2) a polycondensation catalyst comprising a hydrolyzate (I-n) obtained by hydrolyzing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound, and
(3) a polycondensation catalyst comprising:
the hydrolyzate (I-m) or (I-n), and
a compound of at least one element selected from beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium and antimony, a phosphate or a phosphite.
In the process for producing a polyester described above, the phosphoric ester is preferably tributyl phosphate, trioctyl phosphate or triphenyl phosphate.
A still further embodiment of the process for producing a polyester according to the present invention is a process comprising polycondensing an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof in the presence of a polycondensation catalyst selected from the following catalysts (1) to (3) and at least one compound selected from cyclic lactone compounds and hindered phenol compounds to produce a polyester;
(1) a polycondensation catalyst comprising a hydrolyzate (I-m) obtained by hydrolyzing a titanium halide,
(2) a polycondensation catalyst comprising a hydrolyzate (I-n) obtained by hydrolyzing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound, and
(3) a polycondensation catalyst comprising:
the hydrolyzate (I-m) or (I-n), and
a compound of at least one element selected from beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium and antimony, a phosphate or a phosphite.
In the process for producing a polyester described above, at least one phosphorus compound selected from phosphoric acid and phosphoric esters can be further used in combination.
The at least one compound selected from cyclic lactone compounds and hindered phenol compounds is preferably a mixture of 5,7-di-t-butyl-3-(3,4-dimethylphenyl)-3H-benzofuran-2-one, tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane and tris(2,4-di-t-butylphenyl)phosphite.
A still further embodiment of the process for producing a polyester according to the present invention is a process comprising an esterification step in which an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof are esterified to form a low condensate and a polycondensation step in which the low condensate is polycondensed in the presence of a polycondensation catalyst to increase the molecular weight, wherein:
the polycondensation catalyst used is a catalyst comprising:
(I) a polycondensation catalyst component comprising a hydrolyzate (I-m) obtained by hydrolyzing a titanium halide or a hydrolyzate (I-n) obtained by hydrolyzing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound, and
(II) a co-catalyst component comprising a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimony and phosphorus; and
a tint adjusting agent is added in the esterification step or the polycondensation step.
In the process for producing a polyester described above, the tint adjusting agent is preferably at least one agent selected from Solvent Blue 104, Pigment Red 263, Solvent Red 135, Pigment Blue 29, Pigment Blue 15:1, Pigment Blue 15:3, Pigment Red 187 and Pigment Violet 19.
The co-catalyst component (II) is preferably a magnesium compound.
Embodiments of the method for treating a polyester according to the present invention include:
a method for treating a polyester, comprising bringing a polyester, which is obtained by the use of a titanium compound catalyst and in which the reaction has been completed, into contact with a phosphorous acid aqueous solution, a hypophosphorous acid aqueous solution, a phosphoric ester aqueous solution, a phosphorous ester aqueous solution or a hypophosphorous ester aqueous solution, each of said solutions having a concentration of not less than 10 ppm in terms of phosphorus atom;
a method for treating a polyester, comprising bringing a polyester, which is obtained by the use of a titanium compound catalyst and in which the reaction has been completed, into contact with an organic solvent; and
a method for treating a polyester, comprising bringing a polyester, which is obtained by the use of a titanium compound catalyst and in which the reaction has been completed, into contact with an organic solvent solution of phosphoric acid, an organic solvent solution of a phosphoric ester, an organic solvent solution of phosphorous acid, an organic solvent solution of hypophosphorous acid, an organic solvent solution of a phosphorous ester or an organic solvent solution of a hypophosphorous ester, each of said solutions having a concentration of not less than 10 ppm in terms of phosphorus atom.
The polyester preferably has an intrinsic viscosity of not less than 0.50 dl/g, a density of not less than 1.37 g/cm3 and an acetaldehyde content of not more than 5 ppm.
The organic solvent is a solvent selected from alcohols, saturated hydrocarbons and ketones, preferably isopropanol or acetone.
The phosphoric ester is preferably tributyl phosphate, triphenyl phosphate or trimethyl phosphate.
The polyester used in the above method is preferably polyethylene terephthalate.
One embodiment of the polyester according to the present invention is a polyester (P-1) obtained by polycondensing an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof in the presence of a catalyst for polyester production which comprises:
(I) a polycondensation catalyst component comprising the solid titanium compound (I-c) or the titanium-containing solid compound (I-d), and
(II) a co-catalyst component comprising a magnesium compound,
wherein the titanium content is in the range of 1 to 100 ppm, the magnesium content is in the range of 1 to 200 ppm, and the weight ratio (Mg/Ti) of magnesium to titanium is not less than 0.01.
The polyester (P-1) is preferably polyethylene terephthalate.
Another embodiment of the polyester according to the present invention is a polyester (p-2) having the following properties:
a titanium atom is contained in an amount of 0.1 to 200 ppm,
a metal atom M selected from beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc and antimony is contained in an amount of 0.1 to 500 ppm,
the molar ratio (titanium atom/metal atom M) of the titanium atom to the metal atom M is in the range of 1/50 to 50/1, and
a tint adjusting agent is contained in an amount of 0.01 to 100 ppm.
The polyester (P-2) is preferably polyethylene terephthalate.
A further embodiment of the polyester according to the present invention is a polyester (p-3) having the following properties:
the intrinsic viscosity is not less than 0.50 dl/g,
a titanium atom is contained in an amount of 0.1 to 200 ppm,
a metal atom M selected from beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc and antimony is contained in an amount of 0.1 to 500 ppm,
the molar ratio (titanium atom/metal atom M) of the titanium atom to the metal atom M is in the range of 0.05 to 50, and
the content of acetaldehyde is not more than 4 ppm, and when this acetaldehyde content is taken as W0 ppm and a content of acetaldehyde in a stepped square plate molded product obtained by heating said polyester to a temperature of 275xc2x0 C. to melt it and molding the molten polyester is taken as W1 ppm, the value of W1-W0 is not more than 10 ppm.
In the polyester (P-3), the titanium atom is preferably one derived from a polycondensation catalyst obtained by hydrolysis of a titanium halide.
The polyester (P-3) is preferably polyethylene terephthalate.
A still further embodiment of the polyester according to the present invention is a polyester (P-4) having the following properties:
the intrinsic viscosity is not less than 0.50 dl/g,
a titanium atom is contained in an amount of 0.1 to 200 ppm,
a metal atom M selected from beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc and antimony is contained in an amount of 0.1 to 500 ppm,
the molar ratio (titanium atom/metal atom M) of the titanium atom to the metal atom M is in the range of 0.05 to 50, and
the content of a cyclic trimer is not more than 0.5% by weight, and when this cyclic trimer content is taken as x % by weight and a content of a cyclic trimer in a stepped square plate molded product obtained by heating said polyester to a temperature of 290xc2x0 C. to melt it and molding the molten polyester is taken as y % by weight, x and y satisfy the following relation
yxe2x89xa6xe2x88x920.2x+0.2.
In the polyester (P-4), the titanium atom is preferably one derived from a polycondensation catalyst obtained by hydrolysis of a titanium halide.
The polyester (P-4) is preferably polyethylene terephthalate.
A still further embodiment of the polyester according to the present invention is a polyester (P-5) having the following properties:
when the ratio (L/T) of a flow length (L) to a flow thickness (T) in the injection molding of said polyester at 290xc2x0 C. is taken as Y and the intrinsic viscosity of a molded product obtained by the injection molding is taken as X (dl/g), X and Y satisfy the following relation
Yxe2x89xa7647xe2x88x92500X.
The polyester (P-5) is obtained by, for example, polycondensing an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof in the presence of:
a polycondensation catalyst comprising a hydrolyzate (I-m) obtained by hydrolyzing a titanium halide,
a polycondensation catalyst comprising a hydrolyzate (I-n) obtained by hydrolyzing a mixture of a titanium halide and a compound of at least one element selected from elements other than titanium or a precursor of the compound, or
a polycondensation catalyst comprising:
(I) a polycondensation catalyst component comprising the hydrolyzate (I-m) or the hydrolyzate (I-n), and
(II) a co-catalyst component comprising a compound of at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, barium, boron, aluminum, gallium, manganese, cobalt, zinc, germanium, antimony and phosphorus.
The compound of at least one element selected from elements other than titanium or the precursor of the compound is the same compound or precursor as previously described.
The co-catalyst compound (II) is preferably a magnesium compound.
In the polyester (P-5), it is preferable that the titanium atom content is in the range of 1 to 100 ppm, the magnesium atom content is in the range of 1 to 200 ppm, and the weight ratio (Mg/Ti) of the magnesium atom to the titanium atom is not less than 0.01.
The polyester (P-5) is preferably polyethylene terephthalate.
One embodiment of the polyester molded product according to the present invention is a molded product obtained from the polyester (P-1), and examples of the polyester molded products include a blow molded article, a film, a sheet and a fiber.
Another embodiment of the polyester molded product according to the present invention is a blow molded article obtained from the polyester (P-4) and having a cyclic trimer content of not more than 0.6% by weight.
A further embodiment of the polyester molded product according to the present invention is a blow molded article preform or a blow molded article each of which is obtained from the polyester (P-5).